Abstract:
This award supports a project to constrain the accumulation rate, thickness, and temperature history for Siple Dome using a vertical velocity profile that includes the effects of an evolving fabric on deformation through time, to invert the depth-profile of fabric determined from sonic velocity measurements and grain size observed in thin sections in Siple Dome for the surface temperature and ... accumulation rate changes in the past, focusing on the apparent abrupt climate change events at 22ka and 15ka.

The fabric dataset provides crystal fabric orientations for several numerical experiments of fabric evolution. The experiments examine how differing stress regimes affect variations in crystal fabric. Contained are netCDF format files of crystal orientations, crystal size, crystal dislocation densities, stress profiles, and fabric eigenvalues for each experiment. netCDF is an open-source data format hosted by the University Corporation for Atmospheric Research (UCAR) and resources are freely available from their website:http://www.unidata.ucar.edu/software/netcdf/.

This record includes the model's Matlab code, tested on Matlab versions 2009b and 2011a. The code can take run multiple experiments in parallel but does not require this.

Also included are Matlab codes for generating random distribution of crystals using either the Watson distribution or the uniform (on the surface of the unit sphere) distribution. Matlab codes plotting, contouring Schmidt plots, and calculating fabric area-weighted fabric eigevalues is included.

Purpose:
The intellectual merit of the work is that it will extract past climate information from a number of physical properties of the deep ice using a coupled fabric evolution and ice-sheet flow model. The focus will be on the deep ice-age ice at Siple Dome, where the ice-core record shows puzzling signals and where modeling results imply intriguing deformation patterns. The method will also be applied ... to the records from Byrd Station and Taylor Dome to ultimately form a basis for future analysis of the West Antarctic Divide core. The broader impacts of the project are that it will ultimately contribute to our understanding of the effects of anisotropy on ice flow dynamics in West Antarctica. It will contribute to our understanding of the connection between ice flow and the paleoclimate record in ice cores, particularly with respect to the relationship between the chemical record and ice deformation. And it will contribute a new ice-flow model that includes the effects of anisotropy and fabric evolution.